Printing cylinders



June 19, 1962 w. HOTOP ET AL PRINTING CYLINDERS Filed Dec. 21, 1959Jnvenfors mg United States Patent F 3,039,390 PRINTING CYLINDERS WernerHotop, Heinz-Gunter Meese, and Erwin Masjoshusmann, Dortmund-Aplerbeck,Ulrich Biihle, Schwerte (Ruhr), and Giinter Ginzel, Dortmund-Aplerbeck,Germany, assignors to Deutsche Edelstahlwerke Aktiengesellschaft,Krefeld, Germany Filed Dec. 21, 1959, Ser. No. 861,146

Claims priority, application Germany Dec. 27, 1958 6 Claims. (Cl.101-378) The present invention relates to improvements in printingcylinders as described and claimed in the specification of patentapplication Serial No. 779,949, dated December 12, 1958.

In the said specification a printing cylinder is described and claimedwhich comprises a support and an assembly of magnet elements forming thestereo-holding cylinder surface, the said elements comprising soft ironbars with plate-shaped magnets magnetized across their thicknessapplied, preferably adhesively secured, thereto. The elements arearranged in side-by-side adjacency around the axis of the support sothat edges of the bars at the stereoholding surface present poles aroundthe periphery which alternate in their polarity and each of whichextends in the direction of the cylinder generatrix.

In order to ensure that the magnetizable stereo shall be securely held,as many poles as possible should be provided in close juxtapositionround the periphery. This brings about a distribution of the magneticfield in which the lines of force remain in the immediate vicinity ofthe cylinder surface so that they will then all pass through therelatively thin magnetizable layer of the stereo.

To enable such an assembly to be produced around the support, thesupport may be a cylindrical core shaped with appropriately profiledannular-guides for the correspondingly profiled bars and while magneticprinting cylinders so produced are successful, the cores are somewhatcostly to produce in one piece.

According to the present invention, for the purpose of simplifyingproduction and saving material, the support comprises a shaft havingseparate rings arranged around and secured to it and providing profiledguides adapted to permit the magnet elements, comprising the soft-ironbars and the attached permanent magnets, to be assembled successivelyaround the rings and radially retained. The guides formed by the ringsmay be of dovetail section and preferably they are annular projectionsto co-operate with correspondingly contoured notches or grooves in thesoftiron bars. If then an appropriate gap is provided in the guides, thesoft iron bars of the magnet elements appropriately selected forpolarity may be successively registered with the guides and displacedround the rings about the axis of the shaft until a cylindrical assemblyof the magnet elements with peripherally alternating poles has beenproduced and can serve as the printing cylinder.

Such a separate ring may be provided at each end and so contrived thatrings may be shrunk on to the same which will radially hold the softiron bars in a very tight grip.

In order to improve the rigidity of the cylinder the cavities betweenthe magnet elements, the profiled rings, and the shaft, may then be spunout with a solidifying casting compound, such as a hardenable plastic ora low-melting alloy. It has been found that a cylinder thus constructed,although perhaps the cavities have not been centrifugally filled, iswell capable of sustaining the stresses experienced during the printingprocess and can be economically and simply produced.

3,039,390 Patented June 19, 1962 A preferred embodiment of the inventionwill now be described with reference to the accompanying drawings inwhich FIG. 1 is a longitudinal section, and

FIG. 2 is a section taken on the line AB in FIG. 1.

FIG. 3 is a fragmentary View.

As shown in FIG. 1 three rings 2 are pushed on to a shaft .1 and securedby means of taper keys 3. The two end rings have external extensions 4which form the end faces of the cylinder. The peripheries of the rings 2are formed with dovetail guide sections 5 on to which the soft iron bars6 with permanent magnet plates 7 adhesively aflixed thereto areconsecutively pushed after registering them with a suitable gap 5a inthe guide sections 5. The soft magnetic bars with the attached permanentmagnet plates are assembled together to a cylinder with the rings actingas supports in such a way that a sequence of poles of alternatingpolarity in the peripheral direction will appear. Rings 8 are shrunk onthe extensions 4, the rims 9 of said shrunk rings retaining the softiron bars 6 radially in a tight grip.

When additional rigidity is required, the cavities between the bars 6,the guide and retaining rings 2 and shaft 1 may be filled with a plasticor a low-melting metal.

The magnet elements shown are constructed as described in thespecification of the aforesaid application No. 779,949 and a moredetailed description thereof is therefore not given in thisspecification.

What we claim is:

1. A printing cylinder for supporting a magnetizable flexible stereo,comprising a support and an assembly of magnet elements, said elementscomprising soft iron bars and plate-shaped permanent magnets magnetizedacross their thickness, certain of said magnet elements having the northpole of the magnet at the interface between the magnet and the soft ironbar and the remainder having the south pole at the said interface, saidelements being alternately arranged in adjacency around the axis of thesupport so that the longitudinal edges of the said bars at the saidstereo-holding surface present alternating poles in a cylindricalsurface, means spacing said poles in said surface, said supportcomprising a shaft and a plurality of separate rings secured thereto,said rings having peripheral profiled ring guide means and the saidelements having profiled sections co-operating with said guide meanswhereby the magnet elements have been guided round the ring guide meansinto assembled position and means permitting said elements to be broughtinto guidable relation to said peripheral ring guide means beforemovement therearound.

2. A printing cylinder according to claim 1, said separate ringsincluding end rings, said end rings having axial extensions, andretaining rings shrunk onto the said extensions, the said retainingrings having rims which securely radially retain the magnet elementsagainst outward displacement.

3. A printing cylinder according to claim 1, said guide means beingformed by annular projections of the rings and of dove-tailcross-section and said magnet elements having co-operating dovetailnotches, said projections providing a local gap for registering themagnet elements one by one with the said projections for assembly.

4. A printing cylinder according to claim 1, in which internal cavitiesare formed between the magnet elements, the said rings and the saidshaft and a solidifying casting composition has been spun out in thesaid cavities and 3 has hardened to give additional rigidity to theassembly of magnet elements.

5. A printing cylinder according to claim 4 in which the saidcomposition is a plastic.

6. A printing cylinder according to claim 4, in which the saidcomposition is a metal alloy.

References Cited in the file of this patent UNITED STATES PATENTS332,998 Coupland Dec. 22, 1885 4 Baker June 15, 1886 Condon et a1 Dec.21, 1897 Price June 18, 1901 Trist Ian. 24, 1928 Trist July 4, 1933Horst May 6, 1958 FOREIGN PATENTS Germany May 16, 1957

